. >> president obama says he believes chances for comprehensive nuclear agreement with iran are 50/50 at best. >> but what i've consistently said is even as i don't take any options off the table, what we do have to test is the y at we can resolve this issue diplomatically. >> and the president made those comments while participating in a think tank panel on saturday. >>> now to the incredible outpouring of emotion and worship in south africa today. millions of people, regardless of their race, color, or religion, unified in prayer, song, and remembrance in honor of nelson mandela. today's national day of prayer and reflection marks the beginning of a week-long program of mourning in his memory. let's go right now to nbc's michelle koh zin ski, who's in the middle of it all. michelle, a good evening your time. what are we seeing? >> reporter: hi, alex. right here this was a fence lined with some flowers outside the mandela property. now it has become several large hills full of flowers lined with people. you can imagine in churches around the world today mandela was mentioned. here to